Design and Analysis of Cyclone Seperator

Design and Analysis of Cyclone Seperator

Bharath Raj Reddy Dere1

1Mechanical department

Chaitanya Bharathi Institute Of Technology

Hyderabad,India.

A . Divya Sree3,



Hyderabad,India.

Email

G. Mahesh Babu

2,



Hyderabad,India

S. Rajiv Rao4



Hyderabad,India.

ABSTRACT: The gas-solids cyclone separator is industrial

equipment that has been widely used. Due to its industrial

relevance, a large number of computational studies have been

reported in the literature aimed at understanding and

predicting the performance of cyclones in terms of pressure

and velocity variation. One of the approaches is to simulate

the gas-particle flow field in a cyclone by computational fluid

dynamics (CFD).

The cyclone performance parameters are governed

by many operational parameters (e.g., the gas flow rate and

temperature) and geometrical parameters. This study focuses

only on the effect of the geometrical parameters on the flow

field pattern and performance of the tangential inlet cyclone

separators using, CFD approach. The objective of this study is

three-fold. First, to study the optimized stairmand’s design by

understanding the pressure and velocity variations. Second, to

study the performance of a cyclone separator by varying its

geometrical parameters. Third, to study the performance of a

cyclone separator by varying its flow temperatures. Finally to

study the performance of a cyclone separator with collector

and compare to that without collector. Four geometrical

factors have significant effects on the cyclone performance

viz., the inlet width, the inlet height and the cyclone total

height. There are strong interactions between the effect of

inlet dimensions and the vortex finder diameter on the cyclone

performance. In this study, inlet geometry, cone- tip diameter,

cone height is taken for analysis.

The modeling of the cyclonic flow by

computational fluid dynamics (CFD) simulation has been

reported. The effect of the cone tip-diameter, cone height and

inlet geometry in the flow field and performance of cyclone

separators was investigated because of the discrepancies and

uncertainties in the literature about its influence. The flow

field pattern has been simulated and analyzed with the aid of

velocity components and static pressure contour plots. The

CFD model was used to predict the pressure and velocity

variations of cyclone geometries based on Stairmand’s high

efficiency design.

1. MODELLING

1.1 THE STAIRMAND OPTIMIZED DESIGN

Stairmand’s conducted so many experiments on

the cyclone separator and finally developed the optimized

geometrical ratios. By considering this geometric ratio’s

the modeling of the cyclone done in solid works.

.

Figure 1.1.1: cyclone geometry in solid works

TABLE 1: Cyclone geometry used in this simulation (stairmand’s

optimized design) Geometry a/D b /D D

x/D

S /D h /D H

/D

B /D

Stairmand’s

High Efficiency

0.5 0.2 0.5 0.5 1.5 4 0.375

1.2. MODELLING IN SOLID WORKS

To design the cyclone the diameter (D) is

considered as 20 mm.

Step 1: Draw the sketch according to the stairmand’s ratios.

Step 2: specify the dimensions.

Step 3: Revolve the sketch 360 degrees and give thickness

as 0.1mm.

Step 4: to get the inlet, draw a rectangle on the part which

is developed by revolving.

Step 5: extrude the rectangle along the Z-axis (L=D).

Step 6: draw a rectangle on the extruded plan to get the

hallow inlet. Select the rectangle and give extrude cut

throughout the extruded rectangle.

Step 7: save the geometry.

International Journal of Engineering Research & Technology (IJERT)

Vol. 3 Issue 8, August - 2014

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(This work is licensed under a Creative Commons Attribution 4.0 International License.)

12

Fig 1.2.1 shows the dimensions of the cyclone separator

Fig.1.2.2 cyclone separator design.

Fig.1.2.3 Half sectional view of cyclone.

2.

GOVERNING EQUATIONS

2.1 CONTINUITY EQUATION

The continuity equation describes the conservation of

mass.

Consider a differential control volume

Let ‘ρ’ be the density of fluid, ‘u’ be the x-component, ‘m’

be the mass of fluid element

dxdydz)]

x(/=[m

a=

(density) b=u (velocity)

a’= dxx)/( b’=u+ dxxu )/(

fig.4.1.1 fluid particle differential control volume

0]=

)V(

.+t /

[

0=w)z(/ +v)y(/ +u)x(/+t /

0=dzdy dx

w)z(/+dzdy dx

v)y(/

+

dzdy dx

u)x(/+

dz)dy dx t(/

0=efflux

Mass

+onaccumulati

of

Rate

Since,

dzdy dx

w)z(/=direction-in xefflux

Mass

dzdy dx

v)y(/=direction-in xefflux

Mass

dxdydz

u)x(/ =direction-in xefflux

Mass

dz)dy dx

t(/=

volumealdifferenti

mass

of

change

of

Rate



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]W+Q=E[

dxdy yx)]u+yyy(v/ +xy)v+xxx(u/

+vfy+[ufx = )W( done work of rate Total

forces) surfaceby done(work

+ forces)body by done(work =done work Total

y x velocitForce=done work of Rate

dxdy ]yT/?+xT/K[ =Q

n)(conductiogradient etemperatur

due surface acrossfer heat trans gConsiderin

?dxdy v^2)]+(u^2 1/2+[eD/Dt =

element fluid ofenergy totalchange of Rate

v^2)]+(u^2 1/2+[eD/Dt =massunit

per element fluid ofenergy totalchange of Rate

v^2)+(u^2 1/2+e=

massunit per fluid ofenergy Total = E

]W+Q=E[

dW/dt+dQ/dt =dE/dt

forces surface

andbody todueelement fluidon done work of rate

+element fluid intoheat offlux Net

=element fluid theinsideenergy of change of Rate

element. fluid moving a toamics thermodynof law -I g

applyinby derived becan equation energy The

EQUATION ENERGY 2.2

2222

]yT/+xT/K[ = y]T/ v+x

Tu

t

T[ C

]yT/+xT/K[ =DT/Dt C

y)v/+x u/ ( =yx=xy

yv/ =yy

xu/ =xx have We

yxy u/+xy x v/ +yy y v/

+xx x u/ + ]yT/+xT/K[ ==De/Dt

yx)]dxdyu+yyy(v/ +xy)v+xxx(u/

+vfy+[ufx +dxdy ]yT/+xT/K[

=v^2)]dxdy +(u^2D/Dt 1/2+[De/Dt

2222

P

2222

P

2222

2222

2.3 Significance of k-ɛ equation

K-epsilon (k-ε) turbulence model is the most

common model used in Computational Fluid

Dynamics (CFD) to simulate turbulent conditions. It is a

two equation model which gives a general description

of turbulence by means of two transport equations (PDEs).

The original impetus for the K-epsilon model was to

improve the mixing-length model, as well as to find an

alternative to algebraically prescribing turbulent length

scales in moderate to high complexity flows. The first

transported variable determines the energy in

the turbulence and is called turbulent kinetic energy (k).

The second transported variable is the turbulent dissipation

( ) which determines the rate of dissipation of the

turbulent kinetic energy.

3 .CFD ANALYSIS

3.1 STAIRMAND’S OPTIMIZED DESIGN

ANALYSIS: Open Ansys work bench and Select fluent

analysis system for the current analysis.

Fig.3.1.1. fluent project schematic

3.1.1 CYCLONE GEOMETRY

Import the cyclone design from the solid works.

open the design modeler. Click on generate the imported

geometry appears. Select the part body in the tree outline

.select the body click on the screen. Change the solid body

into the fluid body. Close the design modeler and save the

project.

Fig.3.1.2: solid cyclone geometry for the simulation.

3.1.2 MESH

Open mesh.>create named sections

1. Select the inlet face.name it as velocity inlet

2. Select the outlet face and name it as pressure outlet.

3. Select the rest of the faces and name them as wall.

Select mesh in tree outline. In mesh details default

conditions are set to be CFD and FLUENT solver as shown

in the fig 5.1.3. Give high smoothing condition and fine

relevance. And change the transition slow to fast to reduce

the no. of elements. Select mesh and click generate mesh to

obtain mesh. The generated mesh contains 74128



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tetrahedron elements and 14577 nodes. Close the mesh and

update the mesh in project schematic.

Fig.3.1.3: mesh details and no of elements

Fig3.1.4: mesh top view

Fig 3.1.5: mesh front view

3.1.3 SETUP

Double click on the fluent set up to set the

simulation conditions. The software automatically

recognizes the 3d dimension. The display mesh after

reading, embed graphics windows and work bench color

scheme must be enabled. Enable the double precision and

serial processing options. Then click ok to open the fluent.

Fig. 3.1.6: fluent launcher

STEP 1: General > check mesh (To verify the mesh is

correct or not)

Enable pressure based type, absolute

velocity formulation and transient time steps.

Fig.3.1.7: general conditions

STEP 2: In models select the realizable k-epsilon (2eqn)

model and enable the enhanced wall treatment because the

design contains many walls.

Fig.3.1.8: defining the models

STEP 3: Boundary condition 3.1. Velocity inlet> z-velocity =20 m/s

Turbulence: specification method> k-ɛ model

Fig.3.1.9: inlet velocity boundary conditions.

3.2. Outlet Turbulence: specification method> k-ɛ

model

Backflow Turbulence kinetic energy= 5 m2/s2

Backflow Turbulence dissipation rate=10 m2/s3



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Fig.3.1.10: outlet boundary conditions.

3.3. Wall

Wall motion> stationary wall

Shear condition> no slip

STEP 4: Solution methods

Fig.3.1.11: details of solution methods

STEP 5: Initialization: Select standard initialization and

compute from inlet velocity

Fig.3.1.12: initialization conditions

STEP 6: RUN> Check case>close

Time step size(s) =1; Number of time steps =50; Max.

Iterations / time step = 20 > calculate

Fig.3.1.13: set up for the calculation

3.1.4 SOLUTION

Residuals

Fig.3.1.14 residual graph

The solution is converged at the 355th

iteration.

The vector fig 5.15 shows that the path followed by the

fluid inside the cyclone. The flow follows swirl flow

conditions as explained in the principle of the cyclone

separator. The left side bar shows various velocity ranges.

The color obtained in the vectors show the variation of

velocity at the different sections. The values of the velocity

can be studied from the left side scale. To understand the

complete flow inside the cyclone the contours at the z=0 is

computed. The velocity and pressure contours are shown in

fig 5.1.16. which gives complete flow variation in the

cyclone separator.

Vectors

Fig.3.1.15: vectors of velocity

Pressure- velocity contours

The pressure in the cyclone separator increases

from the center to wall. The maximum and minimum static

pressures are 4.122e+002 (pa) and -6.44e+001 (pa)

respectively. The velocity first increases then decreases

from center to towards wall. The maximum and minimum

velocity magnitudes are 23.62 m/s and 0 m/s respectively.



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Fig.3.1.16: the pressure and velocity contours at the section

Z=0 .

Pressure-velocity charts

The following charts shows the pressure and

velocity variation along the y-axis at different sections. The

graphs are plotted with y-axis as pressure/velocity and x-

axis as radial distance along the x-axis.

Table 2: The sections

SERIES 1 AT Y=0

SERIES 2 AT Y=0.01

SERIES 3 AT Y=0.02

SERIES 4 AT Y= -0.01

SERIES 5 AT Y= -0.02

Graphs: The graphs are drawn by taking y-axis as

pressure/velocity and the x-axis as radial distance along X.

fig.3.1.17: the pressure and velocity graphs at different section along the

y-axis.

3.1.5 RESULTS AND DISCUSSIONS

The stairmand’s optimized design results are

shown in above graphs. To study the variations in pressure

and velocity 5 different sections are created along the y-

axis as shown in the table 5.1.1. The variation in the

pressure and velocity inside the cyclone is shown in the fig

5.1.16 & fig 5.1.17. The solution got converged at the 15th

time step, total time is 15s.

The pressure inside the cyclone along the radial

distance (x-axis) increases from centre to the ends. The

pressure variations are also shown as a graph in fig5.1.17.

The shape of the graph is U which shows the fall down of

pressure at the centre of the cyclone (x=0).

The velocity in the cyclone along the radial

direction first increases and then decreases from centre to

the wall. The shape of the graph is inverted W which

shows the fall down of velocity at the centre and at the

wall. The high velocity obtains in the middle portion of the

centre and the wall.

3.2 TEMPERATURE ANALYSIS

This analysis involves various flow studies at

various temperatures. The stairmand’s design is used for

the simulation in fluent. The same set up is used for the

temperature analysis as the stairmand’s design analysis.

Additional to that energy equation is activated to start the

temperature analysis. In the velocity inlet boundary

conditions the temperature of the inlet flow is added. This

study involves in the simulation of the cyclone at 4

different temperatures. The variations in the pressure and

velocity are noted and compared. The effect of the

temperature is justified.

The analysis is done at the temperatures

290,300,310 & 320 (k).

3.2.1 SOLUTION Table 3: pressure and velocity readings at different temperatures

Temp (k) 290 300 310 320

Maxpressure (pa) 533.5 535.35 522.15 522.6

Mini pressure(pa) -185 -192.7 -194.7 194.7

Maxvelocity (m/s) 25.25 25.22 25.12 25.12

Minivelocity (m/s) 0 0 0 0

Graphs: The graphs are drawn by taking y-axis as

pressure/velocity and the x-axis as radial distance along X.

Graph 3.2.1 The variation of pressure velocity in cyclone and at section

Z=0 .

`Pressure contours

Fig 3.2.1 variation of pressure along the radial distance (x-axis) at z=0.

velocity contours



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Fig 3.2.2 variation of velocity along the radial distance (x-axis) at z=0.


The results are concluded that the cone height has

significant effect on the performance of the cyclone. The

pressure in the cyclone varies along the X-axis as shown in

the contours. The pressure first decreases and then

increases. The minimum pressure occurs at the mid section

(x=0). The graph shows the variation in the pressure along

the radial direction. The curve is in U shape explains the

decrease and increase of pressure. The velocity in the

cyclone first increase from the centre and then decreases at

the wall. The curve will be in M shape or reversed W

shape. The velocity is high at the middle portion of the

center and the wall.

The variation in the flow temperature slightly

varies the pressure for every 20k. The velocity of the flow

doesn’t vary with the temperature. So we can say that the

temperature cannot affect the performance of the cyclone

because of the slight variations we can neglect the effect of

temperature.

3.3 THE ANALYSIS OF STAIRMAND’S DESIGN

WITH COLLECTOR

The collector is the attachment to the cyclone

where the particles are collected. Collector is of any shape

(ex: cube, cylindrical). It locates at the end of the cone tip

and it prevents the re-entertainment of particles. In this

analysis a cube shaped collector is provided at the bottom

(with dimensions 15mm*15mm*15mm). The same set up

is used to simulate the cyclone with collector.

3.3.1CYCLONE GEOMETRY and MESH WITH

COLLECTOR

Fig 3.3.1 geometry of cyclone with collector

Fig 3.3.2 mesh of the cyclone with collector

‘

3.3.2 SET UP IS SAME AS THE STARMAND’S

DESIGN ANALYSIS

3.3.3 SOLUTION

The solution of the simulation of the cyclone with

collector is compared with the cyclone without collector.

The variations in pressure and velocity are noted and

compared & the cyclone performance is justified.

Table 4: The pressure and velocity readings.

Without collector With

collector

Max pressure (pa) 418.5 403.4

Mini pressure (pa) -66.28 -55.11

Maxvelocity (m/s) 23.65 23.5

Minivelocit (m/s) 0 0

Graphs: The graphs are drawn by taking the y-axis as

pressure/velocity and x-axis as radial distance along X

Graph 3.3.1: variation of pressure and velocity.

Pressure contours




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velocity contours














center and the wall.The study shows that the collector

doesn’t have much effect on the cyclone performance.

There are slight variations in the pressure and velocity

which can be neglected.

3.4 INLET GEOMETRY The inlet geometry is one of most important

parameter which affects the cyclone performance. This

study involves with various inlet geometries. By varying

the height and width of inlet the inlet geometry varies. The

analysis of 3 different cyclones with different inlet

geometry is simulated in the fluent. By comparing all the 3

cyclones th ne better design is concluded. The same set up

is used for the simulation as stairmand’s design analysis.

3.4.1 SOLUTION

Table 5: pressure and velocity readings

a=12,

b=6

a=10 ,

b=5

a=8, b=4

Max pressure (pa) 513.5 415.7 334.8

Mini pressure (pa) -102.9 -76.28 -46.68

Maxvelocity (m/s) 24.25 23.84 22.89

Minivelocity (m/s) 0 0 0

Graphs: The graphs are drawn by taking the y-axis as

pressure/velocity and x-axis as radial distance along X

Graphs 3.4.1 the pressure and velocity plots

Pressure contours


Velocity contours














center and the wall.

The inlet geometry is the most important

geometrical parameter of the cyclone design. By varying

the inlet dimensions there is a huge variation in the

pressure and velocity. The maximum pressure in the

cyclone falls drastically by the decrease in the inlet



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dimensions. For every 2mm decrease in the inlet height and

1mm decrease in width gives 20% decrease in the pressure.

By the decrease of this inlet dimensions the pressure drop

also decreases and we can say that the one with minimum

pressure drop is works more efficiently. So the inlet

dimension shows a large effect on the performance of the

cyclone. The velocity also decreases by the increase in the

inlet geometry, if velocity decreases the collection

efficiency decreases so the inlet dimensions must be high.

So the cyclone with the inlet height 10mm and inlet width

5mm is better design.

3.

CONCLUSIONS

After studying the existing literature and

performing analysis on certain cyclone parameters, the

following conclusion can be drawn:

The separation mechanism inside cyclone

separators is not well understood yet, and needs

more investigations.

Nearly all published articles have no systematic

and complete study for the effect of geometrical

parameters on the flow field and performance.

In all operating conditions and cyclone types the

FLUENT CFD was found to be much closer to the

experimental measurement.

This project is done taking into consideration

single parameter at a time, the results may vary if

multiple parameters are considered at a time.

Some parameters have less interest compared with

others like the effect of inlet conditions and

cyclone height.

Ex: 1. A cone is not an essential part for

cyclone operation, whereas it serves the

practical purpose of delivering collect

particles

to the central discharge point.

Ex: 2.Comparison between cyclone with

and without dustbin was done and

observed that a negligible effect of the

dustbin on the performance

REFERENCES

[1] Khairy Elsayed 2011, PhD thesis on Analysis and

Optimization of Cyclone Separators Geometry using RANS

and LES Methodologies. Pages from 20-160. [2] John Anderson 2011, A Text Book on Computational Fluid

Dynamics, vol. 1



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Design and Analysis of Cyclone Seperator